Antireflection film, and image display device

ABSTRACT

Provided is an antireflection film comprising a transparent support, at least one high refractive index layer having a refractive index higher by 0.05 or greater but not greater than 1.5 than that of the transparent support and a low refractive index layer having a refractive index lower by 0.05 or greater but not greater than 2.0 than that of the high refractive index layer, wherein the high refractive index layer contains matting agent particles having an average particle size of 0.3 μm or greater but not greater than 20 μm; and the film has a haze value of 10% or less. This antireflection film has a low reflectance, is clear, has a surface less tinged with white and has reduced color due to interference, so that it is suitably used for image display devices such cathode ray tube display device (CRT), plasma display panel (PDP) and liquid crystal display (LCD). The film is also used for a polarizing plate.

TECHNICAL FIELD

[0001] The present invention relates to an antireflection film which isclear, has a surface not so tinged with white and is improved to haveless interference unevenness; and an image display device using thefilm.

BACKGROUND ART

[0002] In image display devices such as cathode ray tube display device(CRT), plasma display panel (PDP) and liquid crystal display device(LCD), in order to prevent a deterioration in the contrast or reflectionby the display due to reflection of external light, antireflection filmsare usually disposed on the outermost surface of the display as a filmfor reducing a reflectance based on the principle of opticalinterference.

[0003] As a method of forming antireflection films, generally known is amethod of applying an optically functional layer to a transparentsupport. For the purpose of antireflection, a reflectance can bereduced, for example, by disposing a layer (low refractive index layer)having a lower refractive index than that of the transparent support, ordisposing a high refractive index layer over the transparent support andthen laying the low refractive index layer over the high refractiveindex layer. Antireflection films formed by such coating method aresuited for mass production, because they can be produced continuously.

[0004] In antireflection films having, over a transparent support, onlya layer (low refractive index layer) having a refractive index lowerthan that of the transparent support, however, the refractive index ofthe low refractive index layer must be reduced sufficiently in order toreduce the reflectance of the antireflection films. For example, in anantireflection film having triacetyl cellulose as a support and a UVcurable film of dipentaerythritol hexaacrylate as a hard coat layerhaving a low refractive index, the refractive index must be reduced to1.40 or less in order to adjust an average reflectance at 450 nm to 650nm to 1.6% or less. As a material having a refractive index of 1.40 orless, magnesium fluoride and calcium fluoride can be given as examplesof inorganic materials, while fluorine-containing compounds having alarge fluorine content can be given as examples of organic materials.Since fluorine compounds lack cohesive power, a film available therefromhas not sufficient scratch resistance as a film to be disposed on theuppermost surface of a display. For the formation of a film havingsufficient scratch resistance, therefore, a compound having a refractiveindex of 1.43 or greater is required.

[0005] The above-described problems can be overcome by increasing therefractive index of a layer underlying the low refractive index layer,that is, adopting a structure in which a high refractive index layer isdisposed over a transparent support and a low refractive index layer isthen laid over the high refractive index layer. For example, anantireflection film having a low refractive index layer disposed over atransparent support via a hard coat layer is described in JapanesePatent Laid-Open No. Hei 7-287102. Also described in it is that thereflectance can be reduced by increasing the refractive index of thehard coat layer.

DISCLOSURE OF THE INVENTION

[0006] In such antireflection films having a high refractive index layerand a low refractive index layer stacked one after another, interferenceunevenness tends to appear owing to a difference in a refractive indexbetween the high refractive index layer and support. This interferenceunevenness leads to a quality-wise problem, because it is visualized asan irregular color of the film.

[0007] An object of the present invention is to provide anantireflection film having a low reflectance and less interferenceunevenness, or an image display device using this antireflection film.

[0008] The above-described object of the present invention was attainedby the below-described means.

[0009] 1. An antireflection film comprising a transparent support, atleast one high refractive index layer having a refractive index higherby 0.05 or greater but not greater than 1.5 than that of the transparentsupport and a low refractive index layer having a refractive index lowerby 0.05 or greater but not greater than 2.0 than that of the highrefractive index layer, wherein:

[0010] the high refractive index layer contains matting agent particleshaving an average particle size of 0.3 μm or greater but not greaterthan 20 μm; and the film has a Haze value of 10% or less.

[0011] 2. An antireflection film as described above in 1, wherein thefilm thickness of the high refractive index layer is 70% or greater butnot greater than 200% of the average particle size of the matting agentparticles.

[0012] 3. An antireflection film as described above in 1 or 2, whereinthe number of the matting agent particles which protrude from the highrefractive index layer falls within a range of from 5000 particles/mm²or greater but not greater than 100000 particles/mm².

[0013] 4. An antireflection film as described above in 3, wherein thenumber of the matting agent particles which protrude from the highrefractive index layer falls within a range of from 8000 particles/mm²or greater but not greater than 40000 particles/mm².

[0014] 5. An antireflection film as described above in any one of 1 to4, wherein the value S expressing the particle size distribution of thematting agent particles and calculated from the following equation (I):

S=[D(0.9)−D(0.1)]/D(0.5)  Equation (I)

[0015] wherein in the formula (I), D(0.1), D(0.5) and D(0.9) are asdefined below:

[0016] D(0.1): 10% of the integrated value of the volume-equivalentparticle size

[0017] D(0.5): 50% of the integrated value of the volume-equivalentparticle size

[0018] D(0.9): 90% of the integrated value of the volume-equivalentparticle size is 1.5 or less.

[0019] 6. An antireflection film as described above in 5, wherein thevalue S indicating the particle size distribution is 1.1 or less.

[0020] 7. An antireflection film as described above in 6, wherein thefilm thickness of the high refractive index layer is 80% or greater butnot greater than 120% of the average particle size of the matting agentparticles.

[0021] 8. An antireflection film as described above in any one of 1 to7, wherein a surface roughness Ra on the surface of the antireflectionfilm over which the high refractive index layer and the low refractiveindex layer have been disposed by coating is 0.003 μm or greater but notgreater than 0.10 μm.

[0022] 9. An antireflection film as described above in any one of 1 to8, wherein the refractive index of the matting agent particles fallswithin a range of ±0.05 of the refractive index of the high refractiveindex layer.

[0023] 10. An antireflection film as described above in any one of 1 to9, wherein the refractive index of the high refractive index layer is1.6 or greater but not greater than 2.0.

[0024] 11. An antireflection film as described above in any one of 1 to10, wherein the internal haze of the high refractive index layer is 2%or less.

[0025] 12. An antireflection film as described above in any one of 1 to11, wherein the transparent support is made of triacetyl cellulose.

[0026] 13. A polarizing plate having, over at least one side thereof, anantireflection film as described above in any one of 1 to 12.

[0027] 14. An image display device, which comprises, over an imagedisplay surface thereof, an antireflection film having a transparentsupport, at least one high refractive index layer having a refractiveindex higher by 0.05 or greater than that of the transparent support anda low refractive index layer having a refractive index lower by 0.05 orgreater than that of the high refractive index layer, wherein the highrefractive index layer contains matting agent particles having anaverage particle size of 0.3 μm or greater but not greater than 20 μm;and the film has a haze value of 10% or less.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a schematic cross-sectional view illustrating a mainlayer constitution of an antireflection film; and

[0029]FIG. 2 illustrates measuring results of the dependence of arefractive index on wavelength and an interference width which is anindex of the size of interference.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] A principal constitution of the antireflection film of thepresent invention will hereinafter be described with reference to theaccompanying drawings.

[0031]FIG. 1 is a schematic cross-sectional view illustrating a mainlayer constitution of the antireflection film.

[0032] The mode illustrated in (a) of FIG. 1 has a layer constitution ofa transparent support 1, a high refractive index layer 2 and a lowrefractive index layer in the order of mention. The high refractiveindex layer 2 contains matting agent particles 2 therein.

[0033] The transparent support 1, high refractive index layer 2 and lowrefractive index layer 3 each has a refractive index satisfying thebelow-described relations.

[0034] Refractive index of high refractive index layer>refractive indexof transparent support

[0035] Refractive index of high refractive index layer>refractive indexof low refractive index layer

[0036] In the antireflection film as illustrated in FIG. 1(a), the lowrefractive index layer satisfying the below-described equation (1) ispreferred, because it contributes to heightening of the antireflectiveeffects.

mλ/4×0.7<n ₁ <mλ/4×1.3  Equation (1)

[0037] wherein, in the formula (1), m stands for a positive odd number(typically, 1), n₁ represents a refractive index of the low refractiveindex layer, and d₁ represents a film thickness (nm) of the lowrefractive index layer.

[0038] In the present invention, the mode as illustrated in FIG. 1(b) isalso preferred. In FIG. 1(b), the antireflection film has a layerconstitution of a transparent support 1, a hard coat layer 5, a highrefractive index layer 2 and a low refractive index layer 3 in the orderof mention. The high refractive index layer 2 contains matting agentparticles 4. The hard coat layer 5, high refractive index layer 2 andlow refractive index layer 3 each has a refractive index satisfying thebelow-described relation.

[0039] Refractive index of high refractive index layer>refractive indexof hard coat layer

[0040] Refractive index of high refractive index layer>refractive indexof low refractive index layer

[0041] It is also preferred that the refractive index of the highrefractive index layer of the present invention cannot be expressed byonly one value, but the layer may be an uneven refractive index layerwith particles dispersed in the material forming the high refractiveindex layer. In this case, the refractive index of the layer isexpressed by an average refractive index of the matrix portion (in thepresent invention, this means a portion made of the material except thematting agent particles). The material forming the high refractive indexlayer preferably has a refractive index ranging from 1.50 to 2.80.

[0042] It is described in Japanese Patent Application Laid-Open No. Hei8-110401 that when a high refractive index material has a monomer havingat least two ethylenically unsaturated groups and fine particles made ofat least one oxide of a metal selected from titanium, aluminum, indium,zinc, tin and antimony and having a particle size of 100 nm or less, noscattering occurs because the particle size of the fine particles issufficiently smaller than the wavelength of light and it opticallybehaves as a uniform substance.

[0043] [Transparent Support]

[0044] Use of a plastic film as the transparent support is preferred.Examples of a polymer forming the plastic film include cellulose esters(such as triacetyl cellulose and diacetyl cellulose), polyamide,polycarbonate, polyesters (such as polyethylene terephthalate andpolyethylene naphthalate), polystyrene, polyolefin and polynorbornenes(trade name; Arton and Zeonex).

[0045] Of these, triacetyl cellulose, polyethylene terephthalate,polyethylene naphthalate and polynorbornene are preferred, withtriacetyl cellulose being particularly preferred.

[0046] The polymer material used for the transparent support haspreferably a refractive index within a range of from 1.4 to 1.7. Withregards to the refractive index of the above-described polymers, that ofcellulose esters is about 1.4 to 1.5 and that of polyesters is about 1.5to 1.7.

[0047] Use of the antireflection film of the present invention for aliquid crystal display device is especially preferred. When it is usedfor the liquid crystal display device, it is disposed on the uppermostsurface of the display, for example, by disposing an adhesive layer onone side of the device. When the transparent support is made oftriacetyl cellulose, triacetyl cellulose is used as a film forprotecting the deflecting layer of a polarizing plate. Use of theantireflection film of the present invention which has antidazzlingproperty as a protecting film is especially preferred from a cost pointof view.

[0048] As the triacetyl cellulose film, that formed by either one ofsingle-layer flow casting or plural-layer co-flow casting of a triacetylcellulose dope which has been prepared by dissolving triacetyl cellulosein a solvent is preferred. From the viewpoint of environmentalpreservation, a triacetyl cellulose film formed using a triacetylcellulose dope, which has been prepared by dissolving triacetylcellulose in a solvent substantially free of dichloromethane by alow-temperature dissolving method or a high-temperature dissolvingmethod which will be described later, is particularly preferred.

[0049] A triacetyl cellulose made of a single layer is prepared by drumcasting or band casting as disclosed in Japanese Patent ApplicationLaid-Open No. Hei 7-11055, while a triacetyl cellulose made of amultiple layer is prepared by so-called co-casting as disclosed inJapanese Patent Application Laid-Open No. Sho 61-94725, Japanese PatentPublication No. Sho 62-43846 or the like. Described specifically, rawmaterial flakes are dissolved in a solvent such as halogenatedhydrocarbon (such as dichloromethane), alcohol (such as methanol,ethanol or butanol), ester (such as methyl formate or methyl acetate) orether (such as dioxane, dioxolane or diethylene ether). To the resultingsolution, an additive such as plasticizer, ultraviolet absorber,deterioration preventive, lubricant and/or release accelerator is addedto the resulting solution as needed. The resulting solution (which willhereinafter be called “dope”) is cast over a support made of ahorizontal type endless metal belt or a rotary drum by dope feedingmeans (which will hereinafter be called “die”). When a single layer isdesired, a single layer casting of a single dope is carried out, whilewhen a multilayer is desired, a low-concentration dope is co-cast overboth sides of a high-concentration cellulose ester dope. After the filmdried over the support to some extent and thereby imparted with rigidityis released from the support, the film is caused to pass through a dryzone by using a carrying means to remove the solvent.

[0050] Dichloromethane is a typical solvent for dissolving triacetylcellulose therein. Halogenated hydrocarbons such as dichloromethane areusable without any technical problem, but in view of the globalenvironment or working environment, the solvent substantially free of ahalogenated hydrocarbon such as dichloromethane is preferred. The term“substantially free” as used herein means that a percentage of thehalogenated hydrocarbon in the organic solvent is less than 5% by mass(preferably less than 2% by mass).

[0051] For the preparation of a triacetyl cellulose dope by using asolvent substantially free of dichloromethane or the like, use of aspecial dissolution method as described below becomes inevitable.

[0052] A first dissolution method which is called “cooling dissolutionmethod” will be described below.

[0053] Triacetyl cellulose is added in portions to a solvent at atemperature (−10 to 40° C.) near room temperature while stirring. Themixture of triacetyl cellulose and the solvent is then cooled to −100 to−10° C. (preferably from −80 to −10° C., more preferably from −50 to−20° C., most preferably from −50 to −30° C.). The cooling can beconducted in a dry ice-methanol bath (−75° C.) or in a cooled diethyleneglycol solution (−30 to −20° C.). This cooling solidified the mixture oftriacetyl cellulose and solvent. The solid mixture thus obtained is thenheated to 0 to 200° C. (preferably from 0 to 150° C., more preferablyfrom 0 to 120° C., most preferably from 0 to 50° C.), whereby a solutionhaving triacetyl cellulose flowing in the solvent is obtained. Theheating may be attained by allowing the solid mixture to stand at roomtemperature or may be heated in a warm bath.

[0054] A second method which is called “high-temperature dissolutionmethod” will next be described.

[0055] First, triacetyl cellulose is added in portions to a solvent at atemperature (−10 to 40° C.) near room temperature while stirring. Thetriacetyl cellulose solution of the present invention is preferablyobtained by swelling, with triacetyl cellulose, a mixed solventcontaining various solvents. In this method, the concentration oftriacetyl cellulose in the mixed solvent is preferably 30% by mass orless, but it is preferably as high as possible when the dryingefficiency upon film formation is taken into consideration. The mixtureof triacetyl cellulose and the mixed solvent is then heated to 70 to240° C. (preferably 80 to 220° C., more preferably 100 to 200° C., mostpreferably 100 to 190° C.) under pressure of 0.2 MPa to 30 MPa. Sincethe heated solution cannot be applied as is, it must be cooled to atemperature not greater than the boiling point of the solvent having thelowest boiling point among the solvents employed. In this case, it isthe common practice to cool the solution to −10 to 50° C. and cause thepressure to return to a normal pressure. Cooling may be conducted onlyby allowing a high-pressure high-temperature container or line housingthe triacetyl cellulose solution to stand at room temperature or bycooling such an apparatus with a refrigerant such as cooling water.

[0056] The triacetyl cellulose film formed in the above-described manneris preferable, because it does not generate much chips upon processingcompared with films formed in the conventional manner.

[0057] The transparent support preferably has a light transmittance of80% or greater, more preferably 86% or greater; preferably has a haze of2.0% or less, more preferably 1.0% or less; and preferably has arefractive index within a range of 1.4 to 1.7.

[0058] The transparent support of the present invention preferably has afilm thickness of 10 μm or greater but not greater than 300 μm, morepreferably 20 μm or greater but not greater than 200 μm, still morepreferably 30 m or greater but not greater than 120 μm. Particularly ina portable image display device for which thinness is one requirement,the transparent support having a thickness of 60 μm or less ispreferred.

[0059] The transparent support preferably has, disposed thereover, anundercoat layer, antistatic layer, mat layer, slipping layer or the likein order to impart it with functionality.

[0060] [Hard Coat Layer]

[0061] In the antireflection film of the present invention, a hard coatlayer may be disposed as needed between the transparent support and thelow refractive-index layer in order to improve the film strength. Thestrength of the hard coat layer is preferably H or greater in pencilhardness, more preferably 2H or greater, especially preferably 3H orgreater. The refractive index of the hard coat layer of the presentinvention can be adjusted, depending on the refractive index of a layerthereover or the transparent support. The refractive index preferablyranges from 1.45 to 1.70.

[0062] As a compound used for a binder of the hard coat layer, polymershaving a saturated hydrocarbon or a polyether as a main chain arepreferred, of which those having a saturated hydrocarbon as a main chainare more preferred. The binder polymer preferably has a crosslinkedstructure. The polymer having a saturated hydrocarbon as a main chain ispreferably obtained by polymerization reaction of an ethylenicallyunsaturated monomer. In order to obtain a crosslinked binder polymer,use of a monomer having at least two ethylenically unsaturated monomersis preferred. In order to increase the refractive index of the hard coatlayer, incorporation of at least one ring or atom selected from aromaticrings, halogen atoms except fluorine, and atoms such as sulfur,phosphorus and nitrogen in the structure of the monomer is preferred.

[0063] Examples of the monomer having at least two ethylenicallyunsaturated monomers include esters of a polyol and (meth)acrylic acid(such as ethylene glycol di(meth)acrylate 1,4-dichlorohexane diacrylate,pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate,trimethylolpropane tri(meth)acrylate, trimethylolethanetri(meth)acrylate, dipentaerythritol tetra(meth)acrylate,dipentaerythritol penta(meth)acrylate; pentaerythritolhexa(meth)acrylate, 1,2,3-cyclohexane tetra(meth)acrylate, polyurethanepolyacrylate, and polyester polyacrylate), vinyl benzene and derivativesthereof (such as 1,4-divinylbenzene, 4-(vinylbenzoicacid)-2-acryloylethyl ester, and 1,4-divinylcyclohexanone),vinylsulfones (such as divinylsulfone), acrylamides (such asmethylenebisacrylamide) and methacrylamide.

[0064] Specific examples of the high refractive index monomer includebis(4-methacryloylthiophenyl)sulfide, vinyl naphthalene, vinylphenylsulfide, and 4-methacryloxyphenyl-4′-methoxyphenylthioether.

[0065] The polymer having a polyether as a main chain is preferablysynthesized by the ring-opening polymerization of a polyfunctional epoxycompound.

[0066] After application, the monomer having these ethylenicallyunsaturated groups is cured by the polymerization reaction by ionizingradiation or heat.

[0067] Of the polymerization reactions of the polyfunctional monomer,that using a photopolymerization initiator is particularly preferred.Examples of the photopolymerization initiator include acetophenones,benzophenones, Michler's benzoyl benzoate, α-amyloxyme ester,tetramethylthiuram monosulfide and thioxanthones.

[0068] In addition to the photopolymerization initiator, aphotosensitizer may be employed. Examples of the photosensitizer includen-butylamine, triethylamine, tri-n-butylphosphine, Michler's ketone andthioxanthone.

[0069] The photopolymerization initiator is added preferably in anamount ranging from 0.1 to 15 parts by mass relative to 100 parts bymass of the polyfunctional monomer, with a range of from 1 to 10 partsby mass being more preferred. The photopolymerization reaction ispreferably carried out by exposing the hard coat layer to ultravioletrays after application and drying.

[0070] Instead of or in addition to the monomer having at least twoethylenically unsaturated groups, a crosslinked structure may beintroduced into the binder polymer by the reaction of a crosslinkablegroup.

[0071] Examples of the crosslinkable functional group include anisocyanate group, an epoxy group, an aziridine group, an oxazolinegroup, an aldehyde group, a carbonyl group, a hydrazine group, acarboxyl group, a hydroxy group, a methylol group, an active methylenegroup and metal alkoxide groups such as alkoxysilyl group. Vinylsulfonicacid, an acid anhydride, a cyanoacrylate derivative, melamine,etherified methylol, an isocyanate compound or a metal alkoxide such astetramethoxysilane can be added for introducing a crosslinked structure.A functional group which exhibits crosslinking property as a result ofthe decomposition reaction, such as block isocyanate group, may also beused. In the present invention, the crosslinkable group is not limitedto the above-described ones but those exhibiting reactivity as a resultof the decomposition of the above-described functional group may beused. Compounds having such a crosslinkable group must be crosslinked byheat or the like after application.

[0072] To the hard coat layer, inorganic fine particles may be added inorder to heighten the curing strength of the film. As the inorganicparticles, those having an average particle size of 0.5 μm or less,especially 0.2 μm or less are preferred.

[0073] Examples of the inorganic fine particles include silicon dioxideparticles, titanium dioxide particles, zirconium dioxide particles,aluminum oxide particles, tin oxide particles, calcium carbonateparticles, barium sulfate particles, talc, kaolin and calcium sulfateparticles. Of these, silicon dioxide particles, titanium dioxideparticles and aluminum oxide particles are particularly preferred. Thesefine particles are preferably surface-treated to increase stability inthe coating solution and heighten the film strength.

[0074] The refractive index of the hard coat layer can be heightened.For this purpose, the hard coat layer preferably contains fine particlesmade of oxides with at least one metal selected from titanium,zirconium, aluminum, indium, zinc, tin and antimony and having aparticle size of 100 nm or less, preferably 50 nm or less. Examples ofthe fine particles include TiO₂, ZrO₂, Al₂O₃, In₂O₃, ZnO, SnO₂, Sb₂O₃and ITO.

[0075] The hard coat layer is preferably imparted with conductivity. Forthis purpose, addition of conductive inorganic fine particles ispreferred. The conductive inorganic fine particles have preferably aparticle size of 500 nm or less, preferably 100 nm or less, especiallypreferably 50 nm or less. Examples of the conductive inorganic fineparticles include tin oxide, indium oxide, zinc oxide and titaniumnitride, of which tin oxide and indium oxide are particularly preferred.The conductive inorganic fine particles have, as a principal component,an oxide or nitride of these metals and may contain another element. Theterm “principal component” means a component whose content (% by mass)is the greatest of all the components constituting the particles.Examples of the another element include Ti, Zr, Sn, Sb, Cu, Fe, Mn, Pb,Cd, As, Cr, Hg, Zn, Al, Mg, Si, P, S, B, Nb, In, V and halogen atoms.When tin oxide or indium oxide is employed, addition of Sb, P, B, Nb,In, V or a halogen atom is preferred in order to heighten theconductivity. As the conductive inorganic fine particles, Sb-containingtin oxide (ATO) and Sn-containing indium oxide (ITO) are particularlypreferred. The percentage of Sb in ATO is preferably 3 to 30% by mass,while the percentage of Sn in ITO is preferably 5 to 20% by mass.

[0076] The inorganic fine particles is added to the hard coat layerpreferably in an amount of from 10 to 90% by mass, more preferably from20 to 80% by mass, especially preferably from 30 to 60% by mass based onthe total mass of the hard coat layer. The thickness of the hard coatlayer is preferably from 1 to 15 μm.

[0077] [High Refractive Index Layer]

[0078] In the present invention, a high refractive index layer isdisposed over the transparent support or transparent support havingthereover the hard coat layer in order to reduce a refractive index. Therefractive index of the high refractive index layer in the presentinvention is set higher by 0.05 or greater but not greater than 1.5 thanthat of the transparent support.

[0079] The refractive index of the high refractive index layer ispreferably from 1.55 to 2.30, more preferably from 1.57 to 2.10,especially preferably from 1.57 to 2.10, most preferably from 1.62 to1.90.

[0080] The thickness of the high refractive index layer is preferablyfrom 0.05 μm to 50 μm, more preferably from 0.1 μm to 20 μm, mostpreferably from 0.3 μm to 10 μm.

[0081] The high refractive index layer of the present invention may havea function as a hard coat layer and is preferably imparted with an equallevel of strength to that of the hard coat layer. The strength of thehigh refractive index layer is HB or greater in terms of pencilhardness, more preferably H or greater, and especially preferably 2H orgreater.

[0082] The high refractive index layer of the present inventionpreferably contains inorganic fine particles and a polymer.

[0083] A compound serving as a binder of the high refractive index layeris preferably a polymer having an unsaturated hydrocarbon or polyetheras a main chain, with a polymer having an unsaturated hydrocarbon as amain chain being more preferred. The binder polymer has preferably acrosslinked structure. The polymer having an unsaturated hydrocarbon asa main chain is preferably prepared by the polymerization reaction of anethylenically unsaturated monomer. The crosslinked binder polymer ispreferably obtained by using a monomer having at least two ethylenicallyunsaturated groups. In order to increase the refractive index,incorporation of at least one ring or atom selected from aromatic rings,halogen atoms except fluorine, and atoms such as sulfur, phosphorus andnitrogen in the structure of the monomer is preferred.

[0084] Examples of the monomer having at least two ethylenicallyunsaturated monomers include esters of a polyol and (meth)acrylic acid(such as ethylene glycol di(meth)acrylate 1,4-dichlohexane diacrylate,pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate,trimethylolpropane tri(meth)acrylate, trimethylolethanetri(meth)acrylate, dipentaerythritol tetra(meth)acrylate,dipentaerythritol penta(meth)acrylate, pentaerythritolhexa(meth)acrylate, 1,2,3-cyclohexane tetra(meth)acrylate, polyurethanepolyacrylate, and polyester polyacrylate), vinyl benzene and derivativesthereof (such as 1,4-divinylbenzene, 4-(vinylbenzoicacid)-2-acryloylethyl ester, and 1,4-divinylcyclohexanone),vinylsulfones (such as divinylsulfone), acrylamides (such asmethylenebisacrylamide) and methacrylamides.

[0085] Specific examples of the high refractive index monomer includebis(4-methacryloylthiophenyl)sulfide, vinyl naphthalene, vinyl phenylsulfide, and 4-methacryloxyphenyl-4′-methoxyphenylthioether.

[0086] The polymer having a polyether as a main chain is preferablysynthesized by the ring-opening polymerization of a polyfunctional epoxycompound.

[0087] Use of a crosslinked polymer as a binder of the high refractiveindex layer of the present invention is also preferred. Introduction ofthe crosslinked structure imparts the polymer with a film formingcapacity, thereby reinforcing the strength of the layer.

[0088] Examples of the main chain of the crosslinked polymer includepolyolefins (saturated hydrocarbons), polyethers, polyureas,polyurethanes, polyesters, polyamines, polyamides, and melamine resins.The polyolefin main chain, polyether main chain, and polyurea main chainare preferred. More preferred are polyolefin main chain and polyethermain chain, with the polyolefin main chain being most preferred.

[0089] The crosslinked polymer may contain an anionic group such ascarboxylic acid group (carboxyl), sulfonic acid group (sulfo) andphosphoric acid group (phosphono). Of these, sulfonic acid group andphosphoric acid group are preferred as the anionic group. The anionicgroup may be in the form of a salt. The polymer having an anionic grouppreferably has a crosslinked structure in its main chain. The anionicgroup serves to maintain the dispersed state of the inorganic fineparticles.

[0090] The polymer may further contain another recurring units(recurring units free of an anionic group and a crosslinked structure).As the another recurring unit, those having an amino group or aquaternary ammonium group and those having a benzene ring are preferred.Similar to the anionic group, the amino group or quaternary ammoniumgroup serve to maintain the dispersed state of the inorganic fineparticles.

[0091] As the monomer having an anionic group, or the monomer having anamino group or a quaternary ammonium group, commercially availablemonomers are usable.

[0092] Preferred examples of the commercially availableanionic-group-containing monomer include “KAYAMAR PM-21 and PM-2” (each,produced by Nippon Kayaku Co., Ltd.), “Antox MS-60, MS-2N and MS-NH4”(each, produced by Nippon Nyukazai Co., Ltd.), “Aronix M-5000, M-6000and M-8000 series” (each, produced by To a Gosei Kagaku Kogyo Co.,Ltd.), “Biscoat #2000 series” (produced by of Osaka Organic ChemicalIndustry, Ltd.), “New Frontier GX-8289” (produced by Dai-ichi KogyoSeiyaku Co., Ltd.), “NK Ester CB-1, and A-SA” (each, produced byShin-Nakamura Chemical Co., Ltd.), and “AR-100, MR-100 and MR-200”(each, produced by Daihachi Kagaku Kogyo).

[0093] Preferred examples of the commercially available amino-containingor quaternary-ammonium-containing monomer include “DMAA” (produced byOsaka Organic Chemical Industry, Ltd.), “DMAEA, and DMAPAA” (each,produced by Kohjin Co., Ltd.), “Blemer QA” (produced by NOF), and “NewFrontier C-1615” (produced by Dai-ichi Kogyo Seiyaku Co., Ltd.).

[0094] After application, these monomers having an ethylenicallyunsaturated monomer are cured by the polymerization reaction by ionizingradiation or heat.

[0095] For the formation of the polymer, photopolymerization or thermalpolymerization reaction can be employed and the photopolymerizationreaction is preferred.

[0096] For the polymerization reaction, use of a polymerizationinitiator is preferred. Examples include the above-describedpolymerization initiators and photopolymerization initiators.

[0097] Use of a photopolymerization initiator is particularly preferredfor the polymerization reaction of the polyfunctional monomer. Examplesof the photopolymerization initiator include acetophenones,benzophenones, Michler's benzoylbenzoate, α-amyloxyme ester,tetramethylthiuram monosulfide and thioxanthone. In addition to thephotopolymerization initiator, a photosensitizer may be employed.Examples of the photosensitizer include n-butylamine, triethylamine,tri-n-butylphosphine Michler's ketone and thioxanthone.

[0098] The photopolymerization initiator is preferably used in an amountranging from 0.1 to 15 parts by mass relative to 100 parts by mass ofthe polyfunctional monomer, with an amount ranging from 1 to 10 parts bymass being more preferred.

[0099] The photopolymerization reaction is preferably carried out byexposure to ultraviolet rays after application and drying of the highrefractive index layer.

[0100] As the polymerization initiator, a commercially available one isusable. A polymerization accelerator may be used in addition to thepolymerization initiator. The polymerization initiator andpolymerization accelerator are preferably added in an amount rangingfrom 0.2 to 10% by mass based on the total amount of the monomer.

[0101] The polymerization of the monomer (or oligomer) may beaccelerated by heating the coating solution (monomer-containingdispersion of inorganic fine particles). Or, the polymer thus formed maybe subjected to additional thermosetting reaction by heating afterapplication of the solution and photopolymerization.

[0102] Instead of or in addition to the monomer having at least twoethylenically unsaturated groups, a crosslinked structure may beintroduced into the binder polymer by the reaction of a crosslinkablegroup. Examples of the crosslinkable functional group include anisocyanate group, an epoxy group, an aziridine group, an oxazolinegroup, an aldehyde group, a carbonyl group, a hydrazine group, acarboxyl group, a hydroxy group, a methylol group, an active methylenegroup and metal alkoxide groups such as alkoxysilyl group. Avinylsulfonic acid, an acid anhydride, a cyanoacrylate derivative, amelamine, an etherified methylol, an isocyanate compound, a metalalkoxide such as tetramethoxysilane, or the like can be used forintroducing a crosslinked structure. A functional group which exhibitscrosslinking property as a result of the decomposition reaction, such asblock isocyanate group, may also be used.

[0103] In the present invention, the crosslinkable group is not limitedto the above-described compounds but those exhibiting reactivity as aresult of the decomposition of the above-described functional group maybe used. Compounds having such a crosslinkable group must be crosslinkedby heat or the like after application.

[0104] To the high refractive index layer, inorganic fine particles maybe added to the binder in order to adjust the refractive index. Use ofmetal oxides or sulfides as these fine particles is preferred. Examplesof the metal oxides or sulfides include titanium dioxide (e.g., ofrutile, mixed crystal of rutile/anatase, anatase, amorphous structure),tin oxide, indium oxide, zinc oxide, zirconium oxide, aluminum oxide,antimony oxide, ITO and zinc sulfide. Of these, titanium oxide,zirconium oxide, tin oxide, and indium oxide are particularly preferred.The inorganic fine particles having, as a main component, the metaloxide or sulfide may contain another element. The term of “maincomponent” means a component whose content (% by mass) is the greatestof all the constituents of the particles. Examples of the anotherelement include Ti, Zr, Sn, Sb, Cu, Fe, Mn, Pb, Cd, As, Cr, Hg, Zn, Al,Mg, Si, P and S.

[0105] The inorganic fine particles to be used for the high refractiveindex layer preferably have a refractive index ranging from 1.50 to2.80, with a range of from 1.60 to 2.80 being more preferred.

[0106] As well as the inorganic fine particles exhibiting a highrefractive index, the high refractive index layer may contain anotherfine particles to impart the layer with improved strength and antistaticperformance. Examples of such inorganic fine particles include silicondioxide particles, aluminum oxide particles, tin oxide particles,calcium carbonate particles, barium sulfate particles, talc, kaolin andcalcium sulfate particles.

[0107] In the present invention, the above-described inorganic fineparticles may be subjected to surface treatment. The surface treatmentis conducted using an inorganic compound or an organic compound.Examples of the inorganic compound to be used for the surface treatmentinclude alumina, silica, zirconium oxide and iron oxide. Of these,alumina and silica are preferred. Examples of the organic compound to beused for the surface treatment include polyols, alkanolamines, organicphosphoric acid and salts thereof, stearic acid, silane coupling agentsand titanate coupling agents. Of these, silane coupling agents are mostpreferred. Surface treatment may be conducted using two or more of thesecompounds in combination. The treatment may be conducted using theabove-described ones.

[0108] The inorganic fine particles are preferably in the form of ricegrain, sphere, cube, spindle or amorphous.

[0109] The primary particles of the inorganic fine particles preferablyhave a weight average particle size of from 1 to 100 nm, more preferablyfrom 1 to 70 nm, most preferably from 1 to 50 nm.

[0110] The inorganic fine particles in the coating layer may exist assecondary particles. The secondary particles preferably have a weightaverage particle size of from 1 to 500 nm, more preferably from 5 to 200nm, still more preferably from 10 to 100 nm. The average particle sizeof the inorganic fine particles can be measured by light scatteringmethod or electron micrograph.

[0111] The specific surface area of the inorganic fine particles ispreferably from 10 to 400 m²/g, more preferably from 20 to 200 m²/g,most preferably from 30 to 150 m²/g/.

[0112] The amount of the inorganic fine particles is preferably from 10to 90% by mass, more preferably from 20 to 80% by mass, especiallypreferably from 30 to 70% by mass, each based on the total mass of thehigh refractive index layer.

[0113] Two or more inorganic fine particles may be used in combinationin the high refractive index layer.

[0114] For the high refractive index layer, use of a polymer having arelatively high refractive index is also preferred. Examples of thepolymer having a high refractive index include polystyrene, styrenecopolymer, polycarbonate, melamine resin, phenol resin, epoxy resin, andpolyurethane available by the reaction between a cyclic (alicyclic oraromatic) isocyanate and polyol. The other polymers having a cyclic(aromatic, heterocyclic, or alicyclic) group and polymers having, as asubstituent, a halogen atom other than fluorine also have a highrefractive index. The polymer may be formed by the polymerizationreaction of a monomer in which a double bond has been introduced toenable radical curing.

[0115] The high refractive index layer may be formed using anorganometal compound having a film forming capacity. The organometalcompound dispersible in a proper medium or in the form of a liquid ispreferred. Examples of the organometal compounds include metalalcoholates (such as titanium tetraethoxide, titanium tetra-i-propoxide,titanium tetra-n-propoxide, titanium tetra-n-butoxide, titaniumtetra-sec-butoxide, titanium tetra-tert-butoxide, aluminum triethoxide,aluminum tri-i-propoxide, aluminum tributoxide, antimony triethoxide,antimony tributoxide, zirconium tetraethoxide, zirconiumtetra-i-propoxide, zirconium tetra-n-propoxide, zirconiumtetra-n-butoxide, zirconium tetra-sec-butoxide, zirconiumtetra-tert-butoxide), chelate compounds (such as di-isopropoxy titaniumbisacetylacetonate, di-butoxy titanium bisacetylacetonate, di-ethoxytitanium bisacetylacetonate, bisacetylacetone zirconium, aluminumacetylacetonate, aluminum di-n-butoxide monoethylacetoacetate, aluminumdi-i-propoxide monomethylacetoacetate, tri-n-butoxide zirconiummonoethylacetoacetate), organic acid salts (such as zirconium ammoniumcarbonate), and active inorganic polymers composed mainly of zirconium.

[0116] In the present invention, addition of matting agent particles tothe high refractive index layer brings about effects of light scatteringor internal light scattering due to the surface roughness, therebymaking it possible to reduce the influence of optical interference inthe high refractive index layer which will otherwise occur owing to adifference in the refractive index between the support underlying thehigh refractive index layer and the refractive index layer. If the highrefractive index layer does not contain matting agent particles, thedependence of reflectance on the wavelength greatly fluctuates due tothe optical interference caused by the difference in the refractiveindex between the high refractive index layer and the transparentsupport, resulting in a deterioration in the antireflection effect andat the same time, occurrence of irregular color. In the antireflectionfilm of the present invention, these problems are overcome by theaddition of matting agent particles. Moreover, the surface roughnessformed by the addition of particles is also effective for avoidingdamage due to the contact with another commodity.

[0117] When the haze value of the antireflection film of the presentinvention exceeds 10% by the addition of the matting agent particles,the film seems white and has lowered clearness under strong light owingto transmission and scattering of reflected light. In addition, whensuch a film is disposed over the surface of an image display device,picture elements are enlarged by a lens effect of the surface roughnessformed by the addition of matting agent particles, leading to glaring.The haze value is therefore set at 10% or less, more preferably 7% orless, especially preferably 5% or less, most preferably 3% or less.

[0118] The matting agent particles to be used in the present inventionhave an average particle size of from 0.3 μm or greater but not greaterthan 20 m, more preferably from 0.3 μm or greater but not greater than10 μm, especially preferably from 0.5 μm or greater but not greater than5 μm.

[0119] When the matting agent particles are added to the high refractiveindex layer of the present invention, the thickness of the highrefractive index layer is preferably adjusted to 70% or greater but notgreater than 200% of the average particle size of the matting agentparticles in order to decrease the surface roughness and suppress thehaze value. When the film thickness becomes greater than the averageparticle size of the matting agent particles, the particle sizedistribution of the matting agent particles is widened to incorporatethe particles of a larger particle size in the layer. The film thicknessis more preferably 75% or greater but not greater than 180%, still morepreferably 80% or greater but not greater than 150%, especiallypreferably 80% or greater but not greater than 120%, of the averageparticle size of the matting agent particles.

[0120] The center line average surface roughness Ra within the plane ofthe surface of the antireflection film of the present invention ispreferably from 0.003 μm or greater but not greater than 0.10 μm, morepreferably from 0.005 μm or greater but not greater than 0.08 μm,especially preferably from 0.007 μm or greater but not greater than 0.05μm, most preferably from 0.008 μm or greater but not greater than 0.04μm. This surface roughness can be measured by three-dimensional surfaceroughness meter, atomic microscope, laser interference microscope, orthe like method.

[0121] The matting agent particles of the present invention can suppressinterference unevenness in the high refractive index layer, therebysuppressing irregular color by protruding from the surface of the highrefractive index layer and imparting the surface with irregularities. Ifthe density of irregularities is too low, glaring caused by the lenseffect of the surface roughness becomes worse. If the density of thematting agent particles is too high, on the other hand, the film istinged with white by scattering on the surface. Accordingly, the numberof the matting agent particles protruding from the surface is preferablyfrom 5000 particles/mm² or greater but not greater than 100000particles/mm², more preferably from 7000 particles/mm² or greater butnot greater than 50000 particles/mm², especially preferably from 8000particles/mm² or greater but not greater than 40000 particles/mm². Thenumber of the matting agent particles protruding from the surface can bedetermined by photographing the surface by an optical microscope orelectron microscope and counting the number of the convex portions ofthe matting agent particles.

[0122] The particle size distribution of the matting agent particles ofthe present invention is preferably as narrow as possible, because ifso, irregularities due to the matting agent particles can be formeduniformly and densely on the surface.

[0123] The particle size can be expressed by the value S calculated inaccordance with the below-described equation (I). The smaller the valueS, the narrower particle size distribution the particles have.

S=[D(0.9)−D(0.1)]/D(0.5)  Equation (I)

[0124] wherein, in the formula (I), D(0.1), D(0.5) and D(0.9) are asdefined below:

[0125] D(0.1): 10% of the integrated value of the volume-equivalentparticle size

[0126] D(0.5): 50% of the integrated value of the volume-equivalentparticle size

[0127] D(0.9): 90% of the integrated value of the volume-equivalentparticle size is 1.5 or less.

[0128] In the matting agent particles of the present invention, thevalue S value preferably 1.5 or less, more preferably 1.3 or less,especially preferably 1.1 or less.

[0129] When the matting agent particles have narrow particle sizedistribution with the value S of 1.1 or less, the thickness of the highrefractive index layer is particularly preferably 80% or greater but notgreater than 120% of the average particle size of the matting agentparticles.

[0130] The particle size distribution can be measured by the Coultercounter method, centrifugal separation method, laserdiffraction-scattering method or electron microscopic observationmethod. The particle size and particle size distribution in the presentinvention are expressed by the volume-equivalent particle size (diameterof a sphere having the same volume as the particle). For themeasurement, usable are “Multisizer” (produced by Malvern Instruments),“Coulter Counter N4” (produced by Beckman Coulter, Inc.) and the like.

[0131] As the matting agent particles of the present invention,particles of a resin or inorganic compound are usable. For example,silica particles, TiO₂ particles, alumina particles, zirconia particles,crosslinked acrylic particles, crosslinked polystyrene particles,melamine resin particles, benzoguanamine resin particles, phenol resinparticles, resorcinol resin particles, polyamide resin particles andpolyimide resin particles are preferably employed. The particles may bein either one of true sphere form or amorphous form. Two or moredifferent particles may be used in combination.

[0132] The matting agent particles of the present invention havepreferably a refractive index of 1.5 or greater but not greater than2.7, more preferably 1.55 or greater but not greater than 2.2,especially preferably 1.60 or greater but not greater than 2.0, mostpreferably 1.62 or greater but not greater than 1.90.

[0133] The refractive index of the matting agent particles of thepresent invention is preferably within ±0.05, more preferably ±0.03 orless, especially preferably +0.02 or less, each of the refractive indexof the high refractive index layer in order to reduce light scatteringbetween the matting agent particles and binder.

[0134] The term “refractive index of the high refractive index layer” asused herein means a refractive index of a layer formed by the materials(binder polymer, inorganic fine particles, matting agent particles andthe like) constituting the high refractive index layer except thematting agent particles.

[0135] The internal haze of the high refractive index layer owing tolight scattering between the binder and matting agent particles ispreferably 2% or less, more preferably 1.5% or less, especiallypreferably 1% or less. Such an internal haze can be estimated byforming, over the high refractive index layer containing the mattingagent, a layer free of the matting agent and having the same refractiveindex, thereby causing surface scattering to disappear.

[0136] [Low Refractive Index Layer]

[0137] The low refractive index layer in the present invention ispreferably formed using a fluorine-containing compound which iscrosslinked by heat or ionizing radiation, inorganic or organic fineparticles, a binder and the like. A layer having a void betweenparticles or inside the particle, and a low refractive index layerformed by sol-gel method are also usable.

[0138] The low refractive index layer preferably has a low refractiveindex in consideration of an improvement in antireflection performance,but it is difficult to impart the low refractive index layer withsufficient strength. From the viewpoint of their balance, the refractiveindex of the low refractive index layer is preferably within a range offrom 1.30 to 1.50, more preferably from 1.35 to 1.49. In addition, therefractive index of the low refractive index layer must be lower by 0.05or greater but not greater than 2.0 than that of the high refractiveindex layer.

[0139] Examples of the crosslinkable fluorine-containing polymercompound for use in the low refractive index layer includeperfluoroalkyl-containing silane compounds (such as(heptadecafluoro-1,1,2,2-tetradecyl)triethoxysilane) andfluorine-containing copolymers having, as constituent units thereof, afluorine-containing monomer and a monomer for imparting a crosslinkablegroup.

[0140] The fluorine-containing polymer is preferably synthesized by thepolymerization reaction of a fluorine-containing ethylenicallyunsaturated monomer. Specific examples of the fluorine-containingmonomer include fluoroolefins (such as fluoroethylene, vinylidenefluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene,and perfluoro-2,2-dimethyl-1,3-dioxol), partially or completelyfluorinated alkyl ester derivatives of (meth)acrylic acid (such as“Biscoat 6% M” (produced by Osaka Organic Chemical Industry, Ltd.) and“M-2020” (produced by Daikin Industries, Ltd.)), completely or partiallyfluorinated vinyl ethers, and perfluoropolyether and derivativesthereof. An intended fluorine-containing polymer is available by the(co)polymerization of one monomer or plural monomers used in combinationas any ratio.

[0141] As the fluorine-containing polymer, copolymers of theabove-described fluorine-containing monomer and a monomer free of afluorine atom may be used. No particular limitation is imposed on themonomer used in combination and examples include olefins (such asethylene, propylene, isoprene, vinyl chloride and vinylidene chloride),acrylate esters (such as methyl acrylate, ethyl acrylate and2-ethylhexyl acrylate), methacrylate esters (such as methylmethacrylate, ethyl methacrylate, butyl methacrylate and ethylene glycoldimethacrylate), styrene derivatives (such as styrene, divinylbenzene,vinyltoluene and α-methylstyrene), vinyl ethers (such as methyl vinylether), vinyl esters (such as vinyl acetate, vinyl propionate and vinylcinnamate), acrylamides (such as N-tert-butylacrylamide andN-cyclohexylacrylamide), methacrylamides and acrylonitrile derivatives.

[0142] A polyorganosiloxane may be preferably introduced into thefluorine-containing polymer to impart slipping property. It may beattained by the polymerization of a polyorganosiloxane having, at theterminal thereof, an acrylic group, a methacrylic group, a vinyl ethergroup or styryl group, with the above-described monomer.

[0143] Examples of the monomer for imparting a crosslinkable groupinclude, as well as (meth)acrylate monomers having, in the moleculethereof, a crosslinkable functional group in advance, such as glycidylmethacrylate, (meth)acrylate monomers having a carboxyl group, ahydroxyl group, an amino group or a sulfonic acid group (such as(meth)acrylic acid, methylol (meth)acrylate, hydroxyalkyl(meth)acrylateand allyl acrylate). In the latter case, a crosslinked structure can beintroduced after the copolymerization, which is known in Japanese PatentLaid-Open No. Hei 10-25388 and Japanese Patent Application Laid-Open No.Hei 10-147739.

[0144] As the fluorine-containing polymer, commercially availablematerials are also usable. Examples of the commercially availablefluorine polymer include “Cytop” (produced by Asahi Glass Co., Ltd.),“Teflon AF” (produced by DuPont), polyvinylidene fluoride, “Lumiflon”(produced by Asahi Glass Co., Ltd.) and “Opstar” (produced by JSRCorporation).

[0145] The low refractive index layer made of such a fluorine materialhas preferably a dynamic friction coefficient of from 0.03 to 0.15 andthe contact angle of water thereon is preferably from 90 to 120°.

[0146] Addition of inorganic fine particles to the low refractive indexlayer made of the above-described fluorine material is preferred forimproving strength. As the inorganic fine particles, amorphous ones arepreferably used. They are preferably made of an oxide, nitride, sulfideor halide of a metal, of which the oxide is especially preferred.Preferred examples of the metal atom constituting these inorganiccompounds include Na, K, Mg, Ca, Ba, Al, Zn, Fe, Cu, Ti, Sn, In, W, Y,Sb, Mn, Ga, V, Nb, Ta, Ag, Si, B, Bi, Mo, Ce, Cd, Be, Pb and Ni, withMg, Ca, B and Si being more preferred. The inorganic compound maycontain two metals. A particularly preferred inorganic compound issilicon dioxide, that is, silica.

[0147] The inorganic fine particles have preferably an average particlesize of from 0.001 to 0.2 μm, more preferably from 0.005 to 0.05 μm. Theparticle size of the fine particles are preferably as uniform aspossible (monodisperse or substantially monodisperse).

[0148] The inorganic fine particles are preferably added in an amount offrom 5 to 90% by mass, more preferably from 10 to 70% by mass,especially preferably from 10 to 50% by mass, each based on the totalmass of the low refractive index layer.

[0149] The inorganic fine particles are preferably used after surfacetreatment. The surface treatment can be classified into physical surfacetreatment such as plasma discharge treatment and corona dischargetreatment, and chemical surface treatment with a coupling agent. In thepresent invention, chemical surface treatment using a coupling agent ispreferred. As the coupling agent, organoalkoxy metal compounds (such astitanium coupling agents and silane coupling agents) are preferablyused. If the inorganic fine particles are made of silica, the surfacetreatment with a silane coupling agent is particularly effective.

[0150] As the refractive index layer, a layer containing inorganic ororganic fine particles and having microvoids formed between theparticles or inside the particles is preferably used.

[0151] The microvoids between the particles can be formed by piling uptwo or more fine particles. Microvoids having a porosity of 26 volume %are formed between fine particles by the closest packing of sphericalfine particles (completely monodisperse) having an equal particle size.Microvoids having a porosity of 48 volume % are formed between fineparticles by the simple steric packing of spherical fine particleshaving an equal particle size. Owing to the particle size distributionof the fine particles and existence of microvoids in the particles,however, the porosity of the actual low refractive index layerfluctuates widely from the above-described theoretical value.

[0152] The refractive index of the low refractive index layer can bereduced by increasing the porosity. The size of the microvoids betweenparticles can easily be adjusted to an adequate value (which causesneither light scattering nor problem in the strength of the lowrefractive index layer) by forming the microvoids by piling up the fineparticles and controlling the particle size of the fine particles.Moreover, an optically uniform low refractive index layer which is alsouniform in the size of the microvoids between particles is available bymaking the particle size of the fine particles uniform. This makes itpossible to form the low refractive index layer to be amicro-void-containing porous film microscopically and a uniform filmoptically or macroscopically.

[0153] The microvoids between particles are preferably closed within thelow refractive index layer by the fine particles and polymer. Lightscattering on the surface of the low refractive index layer toward whichvoids are closed is smaller than that on the surface of the lowrefractive index toward which voids are open.

[0154] By forming microvoids, a macroscopic refractive index of the lowrefractive index layer becomes lower than the sum of the refractiveindices of the components constituting the low refractive index layer.The refractive index of the layer corresponds to the sum of therefractive indices per volume of the constituents of the layer. Theconstituents of the low refractive index layer such as fine particlesand polymer have a refractive index greater than 1, while the air has arefractive index of 1.00. So, formation of microvoids makes it possibleto form a low refractive index layer having a markedly low refractiveindex.

[0155] The average particle size of the fine particles is preferablyfrom 0.5 to 200 nm, more preferably from 1 to 100 nm, still morepreferably from 3 to 70 nm, most preferably from 5 to 40 nm. Theparticle size of the fine particles is preferably as uniform as possible(monodisperse).

[0156] As the inorganic fine particles, those made of an oxide, nitride,sulfide or halide of a metal are preferred, with oxides and halidesbeing especially preferred and oxides and fluorides being mostpreferred. Preferred examples of the metal atom constituting theseinorganic compounds include Na, K, Mg, Ca, Ba, Al, Zn, Fe, Cu, Ti, Sn,In, W, Y, Sb, Mn, Ga, V, Nb, Ta, Ag, Si, B, Bi, Mo, Ce, Cd, Be, Pb andNi, with Mg, Ca, B and Si being more preferred. The organic fineparticles are preferably amorphous. Inorganic compounds containing twometals may be used. A particularly preferred inorganic compound issilicon dioxide, that is, silica.

[0157] Microvoids in the inorganic fine particles can be formed, forexample, crosslinking the molecules of silica forming the particles.When the molecules of silica are crosslinked, its volume reduces andparticles become porous.

[0158] The (porous) inorganic fine particles having microvoids can bedirectly synthesized as a dispersion by the sol-gel method (as describedin Japanese Patent Laid-Open No. Sho 53-112732, or Japanese PatentPublication No. Sho 57-9051) or the precipitation method (as describedin “APPLIED OPTICS”, 27, 3356(1988)). The dispersion is also availableby mechanically pulverizing the powder obtained by thedrying•precipitation method. Commercially available porous inorganicfine particles (such as sol of silicon dioxide) are also usable.

[0159] For the formation of the low refractive index layer, themicrovoids-containing inorganic fine particles are preferably used inthe form dispersed in a proper medium. Preferred examples of thedispersing medium include water, alcohols (such as methanol, ethanol andisopropyl alcohol) and ketones (such as methyl ethyl ketone and methylisobutyl ketone).

[0160] The organic fine particles are preferably polymer fine particlessynthesized by the polymerization reaction (such as emulsionpolymerization) of a monomer. These organic fine particles are alsopreferably amorphous. The polymer organic fine particles preferablycontain a fluorine atom. A percentage of the fluorine atom in thepolymer is preferably from 35 to 80% by mass, more preferably from 45 to75% by mass. It is also preferred to form microvoids in the organic fineparticles by crosslinking the polymer constituting the particles,thereby reducing the volume. In order to crosslink the polymer formingthe particles, use of a polyfunctional monomer in an amount of at least20 mole % of the monomer for synthesizing the polymer is preferred. Thisratio of the polyfunctional monomer is more preferably from 30 to 80mole %, most preferably from 35 to 50 mole %.

[0161] Examples of the fluorine-containing monomer to be used for thesynthesis of the above-described organic fine particles and to be usedfor the synthesis of the fluorine-containing polymer includefluoroolefins (such as fluoroethylene, vinylidene fluoride,tetrafluoroethylene, hexafluoropropylene, andperfluoro-2,2-dimethyl-1,3-dioxole), fluorinated alkyl esters of acrylicacid or methacrylic acid, and fluorinated vinyl ethers.

[0162] Copolymers of a fluorine-containing monomer and a fluorine-freemonomer may be used in combination.

[0163] Examples of the fluorine-free monomer include olefins (such asethylene, propylene, isoprene, vinyl chloride, and vinylidene chloride),acrylic esters (such as methyl acrylate, ethyl acrylate, and2-ethylhexyl acrylate), methacrylic esters (such as methyl methacrylate,ethyl methacrylate, and butyl methacrylate), styrene and its derivatives(such as styrene, vinyltoluene, and α-methylstyrene), vinyl ethers (suchas methylvinyl ether), vinyl esters (such as vinyl acetate and vinylpropionate), acrylamides (such as N-tert-butylacrylamide andN-cyclohexylacrylamide), methacrylamides, and acrylonitriles.

[0164] Examples of the polyfunctional monomer include dienes (such asbutadiene and pentadiene), esters of a polyol and acrylic acid (such asethylene glycol diacrylate, 1,4-cyclohexane diacrylate, anddipentaerythritol hexaacrylate), esters of a polyol and methacrylic acid(such as ethylene glycol dimethacrylate, 1,2,4-cyclohexanetetramethacrylate and pentaerythritol tetramethacrylate), divinylcompounds (such as divinylcyclohexane and 1,4-divinylbenzene),divinylsulfone, bisacrylamides (such as methylene bisacrylamide) andbismethacrylamides.

[0165] The void-containing low refractive index layer preferablycontains 5 to 50% by mass of a polymer. The polymer serves to adherefine particles each other and maintain the structure of the lowrefractive index layer containing voids. The amount of the polymer isadjusted to maintain the strength of the low refractive index layerwithout filling the voids. The amount of the polymer is preferably from10 to 30% by mass based on the total amount of the low refractive indexlayer.

[0166] It is preferred to adhere the polymer and the fine particles forimparting the low refractive index layer with necessary strength.Preferred examples of the method include:

[0167] (1) a method of binding the polymer to a surface treatment agentfor the fine particles,

[0168] (2) a method of using fine particles as a core and forming apolymer shell at the periphery of the fine particles, and

[0169] (3) a method of using the polymer as the binder between fineparticles.

[0170] The polymer to be bound with a surface treatment agent of (1) ispreferably the shell polymer of (2) or binder polymer of (3).

[0171] The polymer of (2) is preferably formed at the periphery of thefine particles by the polymerization reaction prior to the preparationof a coating solution of the low refractive index layer.

[0172] The polymer of (3) is preferably formed by adding a monomer to acoating solution of the low refractive index layer and carrying outpolymerization reaction simultaneously with or after application of thelow refractive index layer. Of these methods (1) to (3), two or threemethods are preferably used in combination. Use of the two methods (1)and (3), or the three methods (1) to (3) in combination is particularlypreferred.

[0173] The above-described methods are described in detail in JapanesePatent Application Laid-Open No. Hei 11-6902.

[0174] As a raw material for the low refractive index layer, hydrolyzedpartial condensates (so-called sol-gel films) of an organometal compoundsuch as organosilane are also preferred. Of these, hydrolyzed partialcondensates of an organosilane are preferred because of a low refractiveindex and high film strength, of which photocuring hydrolyzed partialcondensates of an organosilane are more preferred.

[0175] Specific examples of the organosilane include tetramethoxysilane,tetraethoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane,methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane,vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane,phenyltriethoxysilane, CF₃CH₂CH₂Si(OCH₃)₃, CF₃ (CF₂)₅CH₂CH₂Si (OCH₃)₃,γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,γ-aminopropyltrimethoxysilane, γ-trimethoxysilylpropyl isocyanate,γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane,γ-acryloxypropyltrimethoxysilane, dimethyldimethoxysilane,dimethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane,γ-aminopropylmethyltriethoxysilane,7-mercaptopropylmethyldimethoxysilane andγ-methacryloxypropylmethyldimethoxysilane. The present invention ishowever not limited to these examples.

[0176] It is the common practice to use, as a mixture, pluralorganosilanes which are different each other. They are mixed whileadjusting as needed for the purpose of controlling hardness andfragility, and introducing a functional group.

[0177] The hydrolysis condensation reaction of the organosilane can beconducted in a solventless manner or in a solvent. Organic solvents arepreferred as the solvent. Examples include acetone, methyl ethyl ketone,methyl isobutyl ketone, ethyl acetate, butyl acetate, methanol, ethanol,isopropyl alcohol, butanol, toluene, xylene, tetrahydrofuran and1,4-dioxane.

[0178] The hydrolysis condensation reaction is preferably conducted inthe presence of a catalyst. Examples of the catalyst include inorganicacids such as hydrochloric acid, sulfuric acid and nitric acid, organicacids such as oxalic acid, acetic acid, formic acid, methanesulfonicacid and toluenesulfonic acid, inorganic bases such as sodium hydroxide,potassium hydroxide and ammonia, organic bases such as triethylamine andpyridine, metal alkoxides such as triisopropoxyaluminum andtetrabutoxyzirconium, and metal chelate compounds of the metal alkoxidewith ethyl acetoacetate, acetylacetone or the like.

[0179] The hydrolysis condensation reaction is conducted by adding waterin an amount of from 0.3 to 2.0 moles, preferably from 0.5 to 1.0 moleper mole of an alkoxy group and stirring at 25 to 100° C. in thepresence of the above-described solvent and catalyst. The amount of thecatalyst is from 0.01 to 10 mole %, preferably from 0.1 to 5 mole %based on the alkoxy group. The reaction conditions are preferablyadjusted as needed, depending on the reactivity of the organosilane.

[0180] When the hydrolysate of an organosilane and/or partial condensatethereof, so called sol-gel component (which will be hereinafter beadopted), is made photocuring, the sol-gel component preferably containsa compound capable of generating a reaction accelerator by light. Morespecifically, a photoacid generator or photobase generator is preferred.Either one can accelerate the condensation reaction of the sol-gelcomponent. Specific examples of the photoacid generator include benzointosylate, tri(nitrobenzyl)phosphate, diaryliodonium salt andtriarylsulfonium salt, while those of the photobase generator includenitrobenzylcyclohexyl carbamate and di(methoxybenzyl)hexamethylenedicarbamate. Of these, the photoacid generators, more specifically,triarylsulfonium salt, and diaryliodonium salt are more preferred. Asensitizing dye can preferably be used in combination with thesecompounds.

[0181] The amount of the compound which is used in the present inventionand capable of generating a reaction accelerator by light is preferablyfrom 0.1 to 15%, more preferably from 0.5 to 5% based on the whole solidcontent of the coating solution of the low refractive index layer.

[0182] For the low refractive index layer of the present inventioncomprising the sol-gel component, the above-describedfluorine-containing polymer may preferably be added in order to impartantifouling property and slipping property. As the fluorine-containingpolymer, a polymer available by the polymerization of afluorine-containing vinyl monomer is preferred and a polymer having afunctional group capable of forming a covalent bond with the sol-gelcomponent is more preferred from the viewpoints of the compatibilitywith the sol-gel component and film strength.

[0183] [Preparation Method of Antireflection Film, and Others]

[0184] In addition to the above-described components (inorganic fineparticles, polymer, dispersing medium, polymerization initiator, andpolymerization promoter), each layer of the antireflection film or thecoating solution therefor may contain a polymerization inhibitor,leveling agent, thickener, anti-coloring agent, ultraviolet absorber,silane coupling agent, anti-static agent, and adhesion imparting gent.

[0185] Each layer of the antireflection film can be formed by coatingsuch as dip coating, air knife coating, curtain coating, roller coating,wire bar coating, gravure coating, and extrusion coating (U.S. Pat. No.2,681,294). Two or more layers may be simultaneously formed by coating.The method for simultaneous coating is described in U.S. Pat. Nos.2,761,791, 2,941,898, 3508947, and 3526528; and Yuji Harazaki, “CoatingKogaku” pp.²53, Asakura Shoten (1973).

[0186] In the present invention, interference can be estimated bymeasuring the reflectance.

[0187] The “reflectance” here can be determined by measuring a meanreflectance or the like on the mirror surface or integrating sphere at awavelength from 450 nm to 650 nm.

[0188] The antireflection film may be subjected to surface treatment.Examples of such surface treatment include chemical treatment,mechanical treatment, corona discharge treatment, flame treatment, UVtreatment, high frequency treatment, glow discharge treatment, activeplasma treatment, laser treatment, mix acid treatment, andozone-oxidation treatment. The surface treatment may be conducted on thetransparent support or after application thereto of each layer of theantireflection film. In order to adhere the antireflection film of thepresent invention to a polarizing plate, the antireflection film maypreferably be made hydrophilic. Alkali treatment is particularly suitedfor it. When the antidazzle antireflection film of the present inventionuses triacetyl cellulose (TAC) as the transparent support and is usedfor LCD, this “alkali treatment” is usually known as “saponification”and enables adhesion between TAC and the polarizing plate base.

[0189] No particular limitation is imposed on the method of alkalitreatment insofar as it is a method of dipping in an aqueous alkalisolution. The alkali treatment conditions are controlled as neededwithin an extent not causing a large change in the surface shape of theantireflection film. Examples of the aqueous alkali solution includeaqueous sodium hydroxide solution, aqueous potassium hydroxide solutionand aqueous ammonia solution, with an aqueous sodium hydroxide solutionbeing preferred. The concentration of the aqueous alkali solution ispreferably from 0.1 to 25%, more preferably from 0.5 to 15%. The alkalitreatment is conducted at from 10 to 80° C., preferably from 20 to 60°C., for from 5 seconds to 5 minutes, preferably from 30 seconds to 3minutes. The film after the alkali treatment is preferably neutralizedwith acidic water and then rinsed sufficiently with water. The filmafter rinsed with water is provided for the subsequent step aftersufficient drying.

[0190] The saponification as descried above may be conducted in any oneof the following stages, that is, after the formation of theantireflection film of the present invention, in the form of thetransparent support prior to the formation of the antireflection film,and on the way to form the antireflection film.

[0191] Peeling of the antireflection film, and change in opticalproperties or physical properties can be prevented by employing eitherone of the following saponification methods, that is, saponification ofonly a side opposite to the surface side on which the antireflectionfilm has been formed while laminating one side, and saponification byapplying the aqueous alkali solution only to the surface which is to besaponified.

[0192] The antireflection film can be used for an image display devicesuch as a liquid crystal display device (LCD), a plasma display panel(PDP), an electroluminescence display (ELD) or a cathode ray tubedisplay device (CRT). In CRT, PDP, ELD or the like, adhesion of theantireflection film having the transparent support is preferably carriedout by adhering the transparent support side to the image displaysurface of such an image display device directly or via anotherfunctional film.

[0193] When the antireflection film is used for LCD, it is preferredthat the transparent support side of it is adhered to a protecting filmof a polarizing plate or directly to the polarizing plate via anadhesive layer; or the antireflection surface is disposed on theoutermost layer of the image display surface by adhering the transparentsubstrate side of the antireflection film directly to the polarizingplate. Of them, use of the antireflection film of the present inventionas at least one of the two protecting films of the deflecting layer ismost preferred. By using the antireflection film of the presentinvention for the outermost layer, the polarizing plate which is freefrom reflection of external light and excellent in scratch resistanceand antifouling property is available. In the polarizing plate of thepresent invention, the antireflection film also serves as a protectingfilm, whereby a production cost can be reduced.

EXAMPLES

[0194] The present invention will hereinafter be described in detail byExamples. It should however be borne in mind that the present inventionis not limited to or by them.

Example 1

[0195] (Preparation of Matting Agent Particle Dispersions A to L)

[0196] To 80 parts by mass of methyl ethyl ketone were added 20 parts bymass of matting agent particles as shown in Table 1, followed bydispersion in a Polytron homogenizer or sand grinder, wherebydispersions A to L as shown in Table 1 were prepared. Thevolume-equivalent average particle size and particle size distribution Sof the resulting dispersions were measured by “Multisizer” of MalvernInstruments. These results are shown in Table 1. TABLE 1 (Details of thedispersion of matting agent particles) Refractive Average Particle indexof particle size Kind of particles particles size (μm) distribution SDispersion A SX-50H (crosslinked polystyrene) 1.61 0.5 0.8 Dispersion BSX-130H (crosslinked 1.61 1.3 1.0 polystyrene) Dispersion C SX-200H(crosslinked 1.61 2.0 0.5 polystyrene) Dispersion D SX-350H (crosslinked1.61 3.5 0.8 polystyrene) Dispersion E SX-500H (crosslinked 1.61 5.0 0.8polystyrene) Dispersion F SGP-100C (crosslinked 1.61 25 1.3 polystyrene)Dispersion G MX-150H (PMMA) 1.45 1.5 0.5 Dispersion H Epostar L-15(benzoguanamine) 1.68 13 1.4 Dispersion I Epostar MS (benzoguanamine)1.68 1.5 1.5 Dispersion J Eposter S6 (melamine) 1.68 0.4 1.1 DispersionK Eposter S (melamine) 1.68 0.2 1.2 Dispersion L Eposter MS siftedproduct 1.68 1.5 1.0

[0197] (Preparation of Coating Solution A for a High Refractive IndexLayer)

[0198] In 439 g of a 50:50% by mass mixed solvent of methyl ethyl ketoneand cyclohexanone were dissolved 125 g of a mixture of dipentaerythritolpentaacrylate and dipentaerythritol hexaacrylate (DPHA, produced byNippon Kayaku Co., Ltd.) and 125 g ofbis(4-methacryloylthiophenyl)sulfide (MPSMA, produced by SumitomoSeika). To the resulting solution was added a solution obtained bydissolving 5.0 g of a photopolymerization initiator (“Irgacure 907”,produced by Ciba-Geigy) and 3.0 g of a photosensitizer (“Kayacure DETX”,produced by Nippon Kayaku Co., Ltd.) in 49 g of methyl ethyl ketone. Thefilm obtained by application of the solution and ultraviolet curing hada refractive index of 1.60.

[0199] To the resulting solution was added each of the matting agentparticle dispersions A to G shown in Table 1 to give a surface amount ofthe matting agent as shown in Table 2. The mixture thus obtained wasfiltered through a polypropylene filter having a pore size of 30 μm,whereby a coating solution A for a high refractive index layer wasprepared.

[0200] (Preparation of Coating Solution B for High Refractive IndexLayer)

[0201] To a mixed solvent of 104.1 g of methyl isobutyl ketone an 61.3 gof methyl ethyl ketone was added 217.0 g of an MIBK solution (“KZ-7114”,produced by JSR Corporation) of a hard coat material containing adispersion of zirconium dioxide particles having an average particlesize of 20 nm while stirring by an air disper. To the resulting mixturewas added a mixture of dipentaerythritol pentaacrylate anddipentaerythritol hexaacrylate (“DPHA”, produced by Nippon Kayaku Co.,Ltd.) so that the film obtained by application of the solution andultraviolet curing would have a refractive index of 1.61.

[0202] To the resulting solution was added the matting agent particledispersion shown in Table 1 so that the surface amount of the mattingagent particles would be as shown in Table 2, followed by filtrationthrough a polypropylene filter having a pore size of 30 μm, whereby acoating solution B for a high refractive index layer was prepared.

[0203] (Preparation of Coating Solution C for High Refractive IndexLayer for Comparison)

[0204] In 439 g of methyl isobutyl ketone was dissolved 250 g of amixture of dipentaerythritol pentaacrylate and dipentaerythritolhexaacrylate (“DPHA”, produced by Nippon Kayaku Co., Ltd.). To theresulting solution was added a solution obtained by dissolving 7.5 g ofa photopolymerization initiator (“Irgacure 907”, produced by Ciba Geigy)and 5.0 g of a photosensitizer (“Kayacure-DETX”, produced by NipponKayaku Co., Ltd.) in 49 g of methyl isobutyl ketone. The film obtainedby application of the resulting solution and ultraviolet curing had arefractive index of 1.53.

[0205] To the resulting solution was added each of the matting agentparticle dispersions shown in Table 1 so that the amount of the mattingagent particles on the surface would be as shown in Table 2, followed byfiltration through a polypropylene filter having a pore size of 30 m,whereby a coating solution C for a high refractive index layer wasprepared.

[0206] (Preparation of Coating Solution D for Low Refractive IndexLayer)

[0207] To 210 g of a thermally-crosslinkable fluorine-containing polymer(“JN-7228”, solid concentration: 6% by mass, produced by JSRCorporation) having a refractive index of 1.42 were added 15.2 g ofsilica sol (“MEK-ST”, average particle size: 10 to 20 nm, solidconcentration: 30% by mass, produced by Nissan Chemical Industries) and174 g of methyl ethyl ketone. After stirring, the reaction mixture wasfiltered through a polypropylene filter having a pore size of 1 μm,whereby a coating solution D for a low refractive index layer wasprepared.

[0208] (Preparation of Antireflection Film Sample)

[0209] The coating solution for a high refractive index layer obtainedabove was applied to a triacetyl cellulose film (“TAC-TD80U”, producedby Fuji Photo Film Co., Ltd., refractive index: about 1.49) having athickness of 80 μm to give a coating amount as shown in Table 2 by usinga bar coater. After drying at 120° C., the coated layer was exposed toultraviolet rays under illumination of 400 mW/cm² and a dose of 300mJ/cm² by using an air-cooled metal halide lamp (Eyegraphics Co., Ltd.)of 160 W/cm in the atmosphere having an oxygen concentration of 2% orless upon nitrogen purging, whereby the coated layer was cured and ahigh refractive index layer was formed.

[0210] Over the high refractive index layer, the coating solution D fora low refractive index layer was applied by a bar coater. After dryingat 80° C., the coating layer was thermally crosslinked at 120° C. for 10minutes, whereby a low refractive index layer having a thickness of0.096 μm was formed. The details of the samples 1-A to 1-T of theantireflection films thus formed are shown in Table 2. TABLE 2 Example1: Details of Samples Dispersion Thickness of high The number of CoatingRefractive of Average refractive index matting agent Coating RefractiveSurface solution of index of high matting particle layer/particle sizeparticles on the solution for low index of low roughness high refractiverefractive agent size of matting agent surface refractive indexrefractive Ra index layer index layer particles (μm) particles ratio(particles/mm²) layer index layer (μm) Invention 1-A A 1.60 A 0.5 0.859000 D 1.42 0.04 Invention 1-B A 1.60 B 1.3 0.85 9000 D 1.42 0.05Invention 1-C A 1.60 C 2.0 0.85 9000 D 1.42 0.05 Invention 1-D A 1.60 D3.5 0.85 9000 D 1.42 0.04 Invention 1-E A 1.60 E 5.0 0.85 9000 D 1.420.06 Comp. Ex. 1-F A 1.60 F 25 0.85 9000 — — — Comp. Ex. 1-G A 1.60 C2.0 0.6 9000 D 1.42 0.18 Invention 1-H A 1.60 C 2.0 0.75 9000 D 1.420.10 Invention 1-I A 1.60 C 2.0 0.9 9000 D 1.42 0.08 Invention 1-J A1.60 C 2.0 1.0 9000 D 1.42 0.01 Invention 1-K A 1.60 G 1.5 0.85 9000 D1.42 0.05 Invention 1-L B 1.61 C 2.0 0.85 9000 D 1.42 0.05 Comp. Ex. 1-MB 1.61 None None 0.85 — D 1.42 0.001 Invention 1-N B 1.61 C 2.0 0.854000 D 1.42 0.05 Invention 1-O B 1.61 C 2.0 0.85 6000 D 1.42 0.06Invention 1-P B 1.61 C 2.0 0.85 18000 D 1.42 0.04 Invention 1-Q B 1.61 C2.0 0.85 30000 D 1.42 0.03 Invention 1-R B 1.61 C 2.0 0.85 60000 D 1.420.05 Invention 1-S B 1.61 C 2.0 0.85 120000 D 1.42 0.04 Comp. Ex. 1-T C1.53 C 2.0 0.85 9000 D 1.42 0.04

[0211] (Evaluation of Antireflection Film)

[0212] The antireflection film samples thus obtained were evaluated forthe below-described items.

[0213] (1) Average reflectance, Interference width A spectralreflectance at an incident angle of 5° in the wavelength region of 380to 780 nm was measured using a spectrophotometer (manufactured by JASCOCorporation).

[0214] An average reflectance is an average of reflectances in the rangefrom 450 to 650 nm.

[0215] As an index of the intensity of interference, a differencebetween the maximum value and minimum value of the interference wave ata wavelength of 550 nm was measured and this value was designated as aninterference width.

[0216] (2) Refractive Index of Each Layer

[0217] In accordance with the measuring results of the reflectance, therefractive index of each layer was determined by conducting fittingcalculation of the refractive index based on the multiwave interferenceby Fresnel reflection.

[0218] (3) Haze

[0219] The haze of the film obtained as described above was measuredusing a haze meter “MODEL 1001DP” (manufactured by Nippon DenshokuIndustries, Co., Ltd.).

[0220] (4) Internal Haze

[0221] A haze was measured when the surface roughness was eliminated byapplying a coating solution having the same refractive index with thatof a high refractive index layer and being free of matting agentparticles to a sample to which the high refractive index layer had beenapplied.

[0222] (5) Color

[0223] The film prepared as described above was adhered onto apolarizing plate and color of reflected light when viewed at differentangles was judged visually.

[0224] o: having almost no color

[0225] oΔ: having a slight color

[0226] Δ: having a color but not problematic

[0227] x: having a marked color change

[0228] (6) Tinge of White

[0229] The film prepared as described above was adhered to a polarizingplate and it was visually observed whether the surface was tinged withwhite.

[0230] o: clear with high transparency

[0231] oΔ: tinged slightly with white

[0232] Δ: tinged with white but not problematic

[0233] x: tinged with white and inferior in transparency

[0234] (7) Glare of Transmitted Light

[0235] Each of the films thus formed was adhered to a liquid crystalcell having fineness as high as about 200 ppi (200 pixels per inch: 200pixels in a 1-inch square) and the glare of transmitted light wasevaluated according to the following criteria:

[0236] o: Glare was scarcely recognized.

[0237] Δ: Glare was slightly recognized.

[0238] x: Glare was obviously recognized.

[0239] (8) Friction With Steel Wool

[0240] The extent of scratches made by moving a steel wool #0000 backand forth 10 times under a load of 400 g applied to an area of a 10-yencoin was evaluated.

[0241] o: No scratches

[0242] Δ: Some scratches but not clear

[0243] x: Severe scratches

[0244] (9) Pencil Hardness

[0245] After the film formed as described above was allowed to stand for2 hours under the conditions of temperature at 25° C. and relativehumidity of 60%, it was scratched five times with a test pencil asprescribed in JIS S6006 under a load of 500 g in accordance with thepencil hardness evaluation method as prescribed in JIS K5400. Of thepencils which were recognized to make no scratches, the greatest pencilhardness was designated as the pencil hardness of the film.

[0246] In Table 3, evaluation results of the samples of the presentinvention and comparative samples described in Table 2 are shown. It wasimpossible to form an antireflection film by using, of the samples shownin Table 2, Comparative Sample 1-F for which matting agent particleshaving an average particle size of 25 μm had been used, because curlingand film cracks appeared owing to an excessively thick binder film.Evaluation results of it are therefore not included in Table 3. TABLE 3Results of Example 1 Friction Average Tinge with Haze Internalreflectance Interference of steel Pencil (%) haze (%) (%) width Colorwhite Glare wool hardness Invention 3.5 1.1 1.5 1.3 Δ ∘Δ ∘ ∘ H 1-AInvention 3.7 1.3 1.5 0.8 ∘ ∘Δ ∘ ∘ 2H 1-B Invention 3.2 1.2 1.6 0.5 ∘ ∘Δ∘ ∘ 2H 1-C Invention 3.8 1.4 1.4 0.4 ∘ ∘Δ ∘ ∘ 3H 1-D Invention 3.6 1.31.5 0.3 ∘ ∘Δ ∘ ∘ 3H 1-E Invention 12.0 1.2 1.0 0 ∘ x Δ ∘ 2H 1-GInvention 7.0 1.4 1.2 0.3 ∘ Δ Δ ∘ 2H 1-H Invention 2.5 1.3 1.6 0.8 ∘ ∘ ∘∘ 2H 1-I Invention 1.5 1.1 1.8 1.0 ∘Δ ∘ ∘ ∘ 2H 1-J Invention 7.0 4.0 1.50.5 ∘ Δ ∘ ∘ 2H 1-K Invention 2.3 0.4 1.5 0.5 ∘ ∘ ∘ ∘ 2H 1-L Comp. 0.30.1 1.8 1.5 x ∘ ∘ x 2H Ex. 1-M Invention 1.5 0.3 1.6 0.6 ∘ ∘ Δ Δ 2H 1-NInvention 2.0 0.4 1.6 0.5 ∘ ∘ Δ ∘ 2H 1-O Invention 2.5 0.5 1.5 0.5 ∘ ∘ ∘∘ 2H 1-P Invention 2.3 0.4 1.4 0.5 ∘ ∘ ∘ ∘ 2H 1-Q Invention 1.8 0.5 1.40.6 ∘ ∘ ∘ ∘ H 1-R Invention 1.5 0.4 1.4 0.5 ∘ ∘ ∘ ∘ HB 1-S Comp. 4.5 2.52.5 0.8 ∘ Δ ∘ ∘ H Ex. 1-T

[0247] The evaluation results shown in Table 3 have revealed as follows.

[0248] The samples of the present invention exhibited good results ineach of color and tinge of white.

[0249] In the test on tinge of white, Comparative Sample 1-G exhibitinga high haze value, on the other hand, showed inferior results.Comparative Sample 1-M free of matting agent particles was inferior inthe tests on color and friction with steel wool. Comparative Sample 1-Tin which a difference in the refractive index between the highrefractive index layer and support was 0.04, smaller than a valuepredetermined in the present invention exhibited high reflectance andtherefore inferior in antiglare property.

[0250] Samples 1-G to 1-J have revealed that Invention Sample 1-H inwhich the thickness of the high refractive index layer is 70% or greaterof the average particle size of the matting agent particles showed lesstinge of white and Invention Samples 1-1 and 1-J exhibited a lower hazeand less color.

[0251] Samples 1-N to 1-S have revealed that Invention Samples 1-N and1-0 in which the number of the matting agent particles protruding fromthe high refractive index layer was 8000 particles/mm² or less wereinferior in the glare test; Invention Sample 1-N in which the number was5000 particles/mm² or less showed bad results also in the test of thefriction with steel wool; Invention Sample 1-R in which the number ofthe matting agent particles is 40000 particles/mm² or greater andInvention Sample 1-S in which the number of matting agent particles is100000 particles/mm² or greater showed a low pencil hardness. Thegreater the number, the lower the pencil hardness.

[0252] Invention Sample 1-K in which a difference in refractive indexbetween the high refractive index layer and matting agent particles is0.05 or greater and has an internal haze as high as 4% showed not goodresults in tinge with white.

[0253] The surface roughness on the side of each of the inventionsamples to which the high refractive index layer and the low refractiveindex layer were applied was 0.003 or greater but not greater than 0.10μm

Example 2

[0254] In a similar manner to preparation of the coating solution B fora high refractive index layer in Example 1 except that the matting agentparticle dispersions H to L shown in Table 1 were added to give theamount of the matting agent particles (the number of the matting agentparticles protruding from the high refractive index layer) on thesurface as shown in Table 4, followed by filtration through apolypropylene filter having a pore size of 30 μm, whereby coatingsolutions for a high refractive index layer were prepared.

[0255] In a similar manner to Example 1 except for the use of theresulting coating solutions instead, samples of an antireflection filmshown in Table 4 were formed. Although the amount of the matting agentwas fixed in Samples 2-B to 2-G and 2-J to 2-M, the number of mattingagent particles protruding from the surface decreases with an increasein the film thickness of the high refractive index layer in Samples 2-Bto 2-G exhibiting S=1.5, thus having a wide particle size distribution,while in Samples 2-J to 2-M exhibiting S=1.0, thus having a narrowparticle size distribution, the number of the matting agent particlesprotruding from the surface hardly decreases with an increase in thethickness of the high refractive index layer.

[0256] In Table 5, evaluation results of Invention Samples andComparative Samples in Table 4 are shown. TABLE 4 Details (2) of Samplesof Example 2 Dispersion Thickness of high The number of CoatingRefractive of Average refractive index matting agent Coating Refractivesolution of index of high matting particle layer/particle size particleson the solution for low index of low high refractive refractive agentsize of matting agent surface refractive index refractive index layerindex layer particles (μm) particles ratio (particles/mm²) layer indexlayer Invention 2-A B 1.68 H 13 1.5 9000 D 1.42 Invention 2-B B 1.68 I1.5 0.9 18000 D 1.42 Invention 2-C B 1.68 I 1.5 1.0 15000 D 1.42Invention 2-D B 1.68 I 1.5 1.1 12000 D 1.42 Invention 2-E B 1.68 I 1.51.2 9000 D 1.42 Invention 2-F B 1.68 I 1.5 1.5 4000 D 1.42 Invention 2-GB 1.68 I 1.5 2.2 1000 D 1.42 Invention 2-H B 1.68 J 0.4 1.1 9000 D 1.42Comp. Ex. 2-I B 1.68 K 0.2 1.1 9000 D 1.42 Invention 2-J B 1.68 L 1.50.75 12000 D 1.42 Invention 2-K B 1.68 L 1.5 0.85 12000 D 1.42 Invention2-L B 1.68 L 1.5 1.0 12000 D 1.42 Invention 2-M B 1.68 L 1.5 1.1 12000 D1.42 Invention 2-N B 1.68 L 1.5 1.3 12000 D 1.42

[0257] TABLE 5 Results of Example 2 Friction Average Tinge with HazeInternal reflectance Interference with steel Pencil (%) haze (%) (%)width Color white Glare wool hardness Invention 4.0 0.6 1.5 0.4 ∘ ∘Δ ∘ ∘3H 2-A Invention 8.0 0.5 1.5 0.1 ∘ Δ ∘ ∘ 2H 2-B lnvention 6.0 0.7 1.60.3 ∘ ∘Δ ∘Δ ∘ 2H 2-C lnvention 4.0 0.9 1.4 0.5 ∘ ∘Δ Δ ∘ 2H 2-D lnvention2.5 0.8 1.5 0.8 ∘ ∘ Δ ∘ 2H 2-E Invention 1.5 0.6 1.0 1.0 ∘ ∘ Δ ∘ 3H 2-Flnvention 0.6 0.5 1.2 1.3 Δ ∘ Δx ∘ 3H 2-G lnvention 3.0 0.7 1.6 1.2 ∘ ∘∘ ∘ H 2-H Comp. 2.8 0.8 1.8 1.5 x ∘ ∘ ∘ HB Ex. 2-I Invention 6.0 0.7 1.50.1 ∘ ∘Δ ∘ ∘ 2H 2-J Invention 3.0 0.8 1.5 0.4 ∘ ∘ ∘ ∘ 2H 2-K lnvention2.2 0.6 1.7 0.7 ∘ ∘ ∘ ∘ 2H 2-L lnvention 1.5 0.6 1.8 0.9 ∘ ∘ ∘ ∘ 3H 2-Mlnvention 0.9 0.5 1.8 1.2 ∘Δ ∘ ∘ ∘ 3H 2-N

[0258] What have been understood from Tables 4 and 5 will next bedescribed.

[0259] Samples of the invention all exhibited good evaluation resultsboth in color and tinge with white.

[0260] Comparative Sample 2-I in which the average particle size of thematting agent particles is less than 0.3 μm is, on the other hand,inferior in color evaluation owing to a thin film thickness of the highrefractive index layer.

[0261] When the matting agent particles exhibiting S=1.5, thus having awide particle size distribution, the film thickness of the highrefractive index layer must be made greater than the particle size ofthe matting agent particles. Invention Sample 2-G in which the filmthickness corresponds to 200% or greater of the particle size of thematting agent particles is a little inferior in the evaluation resultsof color and glare. Invention Samples 2J to 2N in which the mattingagent particles exhibiting S=1.0, thus having a narrow particle sizedistribution, on the other hand, exhibited good results in the color,tinge with white and glare. Particularly when the thickness of the highrefractive index layer falls within a range of from 0.8 to 1.2 (80% to120%) of the average particle size of the matting agent particles, thesamples exhibit good performance.

[0262] Invention Sample 2-A in which the matting agent particles have aparticle size of 13 μm formed a large curl.

[0263] In the next place, after alkali treatment of the antireflectionfilms of Invention Samples 1-P and 2L, they were cut into antireflectionpolarizing plates, respectively. By using each of these polarizingplates, a liquid crystal display device having the antireflective layer(low refractive index layer) disposed as an outermost layer was formed.The device thus formed was used as a liquid crystal device featuringless color due to reflected light, less glare from external light, notinge of white even under external light in the daytime and highvisibility.

[0264] When the polarizing plate was attached to a liquid crystaldisplay device of a high resolution (200 ppi), good visibility wasattained without glare.

INDUSTRIAL APPLICABILITY

[0265] The antireflection films of the present invention feature a lowreflectance and a less color due to interference and at the same time,their tinge of white and glare are suppressed. Use of these filmstherefore makes it possible to provide an image display device whichovercomes the problems of a color due to reflection, tinge with whiteand glare and in addition, has good visibility without much reflectionof external light.

1. An antireflection film comprising a transparent support, at least onehigh refractive index layer having a refractive index higher by 0.05 orgreater but not greater than 1.5 than that of the transparent support,and a low refractive index layer having a refractive index lower by 0.05or greater but not greater than 2.0 than that of the high refractiveindex layer, wherein the high refractive index layer comprises mattingagent particles having an average particle size of 0.3 μm or greater butnot greater than 20 μm, and the film has a haze value of 10% or less. 2.The antireflection film according to claim 1, wherein a film thicknessof the high refractive index layer is 70% or greater but not greaterthan 200% of the average particle size of the matting agent particles.3. The antireflection film according to claim 1 or 2, wherein a numberof the matting agent particles which protrude from the high refractiveindex layer falls within a range of from 5000 particles/mm² or greaterbut not greater than 100000 particles/mm².
 4. The antireflection filmaccording to claim 3, wherein the number of the matting agent particleswhich protrude from the high refractive index layer falls within a rangeof from 8000 particles/mm² or greater but not greater than 40000particles/mm².
 5. The antireflection film according to any one of claims1 to 4, wherein a value S expressing a particle size distribution of thematting agent particles and calculated from the following equation (I):S=[D(0.9)−D(0.1)]/D(0.5)  Equation (I) wherein in the formula (I),D(0.1), D(0.5) and D(0.9) are as defined below: D(0.1): 10% of anintegrated value of a volume-equivalent particle size, D(0.5): 50% of anintegrated value of a volume-equivalent particle size, and D(0.9): 90%of an integrated value of a volume-equivalent particle size, is 1.5 orless.
 6. The antireflection film according to claim 5, wherein the valueS indicating the particle size distribution is 1.1 or less.
 7. Theantireflection film according to claim 6, wherein a film thickness ofthe high refractive index layer is 80% or greater but not greater than120% of the average particle size of the matting agent particles.
 8. Theantireflection film according to any one of claims 1 to 7, wherein asurface roughness Ra on a surface of the antireflection film over whichthe high refractive index layer and the low refractive index layer havebeen disposed by coating is 0.003 μm or greater but not greater than0.10 μm.
 9. The antireflection film according to any one of claims 1 to8, wherein a refractive index of the matting agent particles fallswithin a range of ±0.05 of the refractive index of the high refractiveindex layer.
 10. The antireflection film according to any one of claims1 to 9, wherein the refractive index of the high refractive index layeris 1.6 or greater but not greater than 2.0.
 11. The antireflection filmaccording to any one of claims 1 to 10, wherein an internal haze of thehigh refractive index layer is 2% or less.
 12. The antireflection filmaccording to any one of claims 1 to 11, wherein the transparent supportis made by triacetyl cellulose.
 13. A polarizing plate comprising theantireflection film according to any one of claims 1 to 12 over at leastone side of the polarizing plate.
 14. An image display device, whichcomprises, on an image display surface thereof, an antireflection filmcomprising a transparent support, at least one high refractive indexlayer having a refractive index higher by 0.05 or greater than that ofthe transparent support and a low refractive index layer having arefractive index lower by 0.05 or greater than that of the highrefractive index layer, the high refractive index layer comprisingmatting agent particles having an average particle size of 0.3 μm orgreater but not greater than 20 μm, and the film having a haze value of10% or less.